#! /bin/bash

val=`expr 2 + 2`
echo "两数之和：$val";

a=10
b=20

val=`expr $a + $b`
echo "a+b: $val";

if [ $a == $b ]
then
  echo "a等于b";
fi

if [ $a != $b ]
then
  echo "a不等于b";
fi

if [ $a eq $b ]
then
  echo "$a等于$b";
else
  echo "$a不等于$b";
fi



